Electrical Machines - Basic vocational knowledge (Institut für Berufliche Entwicklung, 144 p.): 8. Transformer: 8.3. Three-phase transformer: 8.3.6. Technical data of customary transformers

Electrical Machines - Basic vocational knowledge (Institut für Berufliche Entwicklung, 144 p.)

8. Transformer

8.3. Three-phase transformer

		8.3.1. Three-phase transformation with single-phase transformers
		8.3.2. Three-phase transformers
		8.3.3. Vector groups
		8.3.4. Application of three-phase transformers in power supply
		8.3.5. Parallel operation of transformers
		8.3.6. Technical data of customary transformers

8.3.6. Technical data of customary transformers

The surveys 22 and 23 feature the index figures of several mains and distribution transformers.

Survey 22 - Characteristic values of distribution transformers (three-phase oil transformer)

Rated power	kVa	100	160	250	400	630	1000	1600
Rated uppervoltage	kV	(6; 10; 15; 20)		(6; 10; 15; 20; 30)			(6; 10; 15; 20; 30)
Adjustment range	%	± 4		± 5			± 5
Rated undervoltage	kV	(0.231; 0.4; 0.525)		(0.4; 0.525)			(0.4; 0.525; 6.3)
Idling losses	W	380	550	700 (740)	1000 (1050)	1450 (1550)	2200 (2400)	3200 (3400)
Short circuit losses	W	2200 (2300)	2900 (3200)	4400	5900	7800	11000	16000
Short circuit voltage	%	3.8 (4)		6	6	6	6	6
Dimensions length a 1	mm	1110	1260	1810 (1870)	1980 (2040)	2110 (2170)	2300 (2350)	2650 (2800)
width b	mm	640	800	800 (880)	1100	1100	1000	1000
height h₁	mm	1420	1590	1870 (1900)	1950 (2000)	2215 (2255)	2490 (2600)	2700 (2775)
Oil filling	kg	215	300	470 (570)	620 (700)	755 (860)	1150 (1250)	1550 (1750)
total weight	kg	790 (800)	1070 (1080)	1520 (1680)	2020 (2200)	2620 (2850)	4000 (4250)	5750 (5950)
Vector group	-	(Yy0; Yz5)		(Yy0; Dy5)			(Yy0; Dy5)

Survey 23 - Characteristic values of dry-type transformers

Rated power	kVa	63	100	160	250	400	630	1000
Rated upper-voltage	kV	(2; 3; 5; 6; 10; )				(2; 3; 5; 6; 10; )
rated under-voltage	kV	(0,231; 0,4; 0,525)				(0,4; 0,525)
Rated frequency	Hz	(50)				(50)
Idling losses	W	580	750	900	1200	1750	2500	2900
Short-circuit losses	W	1330	1700 (1780)	2570 (2750)	3200	5250	6500	10400
Short-circuit voltage	%	(3, 8(4))				(6)

Figure 146 serves as an example of the dimensional size of a three-phase oil transformer.

Figure 146 - Oil transformer for the 250 - 16000 kVA range

1 Oil level, 2 Thermo-pockets, 3 Oil removal device, 4 Converter, 5 Eye bolt, 6 Earthing screw, 7, 8 Oil opening, 9 Buchholz relay, 10 Stop valves (from 1000 kVA onwards), 11 Shoulder hooks, 12 Hoisting points, 13 Variable dimensions

Questions for revision and control

1. Describe the basic construction and range of a transformer.
2. How can iron and winding losses be determined in a transformer?
3. How can short-circuit voltage be determined?
4. Which factors cause a voltage drop in a transformer?
5. What is the significance of the index figure in vector group data? Which index figures are cited?
6. Which are the most common vector groups and for which purposes are they used?
7. Name the parallel switching conditions.